Indicating apparatus



Oct. 5, 1.948. 1.. LEE, 2D

mmcurme APPARATIE' Filed March 16. 1946 4 Sheets-Sheet 1 I28 IN V EN TOR.

LEE-l7 LE/gH'rm Oct. 5.1948.

Fileql larch 16. 1946 LEE, 2D

INDI OATING APPARATUS 4 shee ts -sheet 3 Oct. 5.194s. LEE, 2D 2,4so;s35

INDICATING APPARATUS Filed Inch 16. 1946 I V 4 Sheets-Shoat 4 Patented on. 5, 1948 to Niles-Bement-Pond Company, West Hartford, Conn., a corporation mesne assignments,

of New Jersey Application March 16, 1946, Serial No. 654,979

28 Claims. 1 The invention relates more particularly to an internal combustion engine fuel supply system adapted for use in or as a part of an airplane, but

.the invention is not necessarily so limited.

One oi the objects of the invention is to provide means which will enable the operator to readily adjust the fuel system formaximum emciency of engine operation.

A further object ofthe invention is to provide means whereby the reading of the needle or other device which indicates efliciency will not be aii'ected by variations in fuel flow corresponding to variations in the torque exerted by the en- 'gine;

A still further object of the invention is to provide an improved means responsive to the rate of fuel flow to the engine, such means being utilized for indicating the maximum efflciency.

Still other objects of the invention are to provide various improved details of structure and arrangement that are useful .or advantageous in attaining the before-stated more general objects.

Further objects of the invention will be apparent from the accompanying drawings and from the following specification and claims.

Of the drawings:

Fig. 1 is a schematic view showing the essential elements associated with and forming parts of the efliciency indicator.

Fig. 2 is a longitudinal sectional view of the indicator unit, this view being'taken along the line 2-2 of Fig. 3.

Fig. 3 is a longitudinal sectional view taken along the line 3-3 of Fig. 2.

Fig. 4 is a transverse sectional view taken along the line 4-4 of Fig. 3.

Fig. 5 is a longitudinal sectional view taken along the line 5 5 of Fig. 4.

1 Fig. 6 is an enlarged fragmentary sectional view taken along the line 66 of Fig. 4.

Fig. 7 is a plan view of the indicator unit. While not necessarily so limited, the invention is particularly applicable to and advantageous for airplane use and it will be so described. Re-

ferring first to Fig. 1 of the drawings, there is shown a body In of a carburetor for an aircraft.

two superchargers may place. I

The Venturi restriction [4 produces a pressure be used, one in each difl'erential between the inlet l2 and the throat of the restriction which varies substantially in accordance withvthe square of the velocity of the air passing through the restriction. Since the cross-sectional area of the venturi is constant, this pressure differential may be taken as a measure of the volume of air flowing through the passage per unit time. In order to obtain a pressure differential varying as a function of the mass of air per-unit time flowing through the venturi M, the pressure differential between the entrance I 2 and the throat of venturi I4 is utilized to create an air flow through a secondary air passage extending from entrance i2 to the throat of venturi I4. A plurality of impact tubes 24 is provided, only one of which is shown, whose open ends project into the entrance I2 to receive the impact of the entering air. The secondary air passage may be traced from entrance l2, through tubes 24, a conduit 26, a conduit having a restriction at 28, a restriction controlled by a valve 30, a chamber 82 and a conduit 34 extending to the throat of the venturi l4. The conduits 26 and 28 are connected respectively with conduits 36 and '38 which communicate with chambers 40 and 42 in a pressure meter indicated generally at 44.

The fuel enters the carburetor from a fuel pump 46 or other source of fuel under superatmospheric pressure. It flows through a conduit 48 to a mixture control unit generally indicated at 50 and a jet system 52, and then through a conduit 54, the pressure meter 44 and a conduit 56 to the fuel discharge nozzle 20. The conduit 48, the mixture control unit 50. the jet system 52 and the conduit 54 will be referred to collectively as the main fuel conduit.

The mixture control unit 50 includes a disc valve 58 fixed on a shaft 60. The disc valve 58 controls the flow of fuel through ports opening into conduits 62 and 64 which lead into the Jet system 52. When the disc 58 is in the position illustrated'in full lines in the drawing, fuel can flow to the jet system only through the conduit 62. This full line position of the disc valve 58 is known as the lean position of the mixture control Bil. When the disc valve 58 is in the dotted line position shown in the drawing, the-fuel can flow through both the conduits 62 and 64. The dotted line position of disc valve 58 is termed the rich position of the mixture control. The disc valve 58 can also be moved to a cut-off" position wherein it cuts off the fiow through both conduits 82 and 84.

The conduit 62 conducts fuel either through a fixed restriction-or jet 88, or through a restriction 88 controlled by an enrichment valve I8 biased to closed position by a spring I2. The conduit 84 conducts fuel to a fixed restriction I4.

Fuel flowing through the restrictions 88 and I4 also flows through another restriction I8 which limits the total fiow through restrictions 68 and I4. The valve 18 is normally closed, but opens at high pressure differentials across the jet system to increase the fuel-to-air ratio under heavy load conditions.

The pressure meter 44 has a diaphragm I8 separating the chambers 48 and 42, this diaphragm being connected with a valve 88. The meter 44 also has a chamber 82 separated from the chamber 42 by a diaphragm 84, and a chamber 88 separated from the chamber 48 by a diaphragm 88. The diaphragms 84 and 88 are also operably connected with the valve 88. The chamber 88 receives fuel from the aforesaid conduit 84, and the downstream side of the valve 88 is connected with the aforesaid conduit 58 leading to the nozzle 28. The chamber 82 is connected by a conduit 88 with the conduit 48 at the upstream side of the Jet system 52.

The pressure in the chamber 82 is the same as that in the fuel line at the upstream side of the Jet system, and the pressure in the chamber 88 is the same as that in the fuel line at the downstream side of the Jet system. The position of valve 88 is determined by the balance between the differential of the pressures in the chambers 48 and 42 acting in the valve opening direction and the differential of the pressures in the chambers 82 and 88 acting in the valve closing direction. Increased air flow results in increased differential between the pressures in the chambers 48 and 42 and causes the valve 88 to move in the opening direction to increase the fuel flow and thus maintain the proper air-to-fuel ratio. However, the increased fuel fiow causes an increased differential of pressures across the Jet system and in the chambers 82 and 88 which tends to move the valve 88 in the closing direction and to establish a new balance between the two differentials.

The before-mentioned valve 38 in the secondary air passage constitutes a second restriction therein, the first restriction being at 28. It will be clear that closing or partial closing of this valve increases the pressure drop at that point, and correspondingly decreases the pressure drop at the restriction 28. Decrease of the pressure drop at 28 decreases the pressure differential on the diaphragm I8 and tends to move the valve 88 in the closing direction, and to thus decrease the fuel flow in the manner already described, Similarly, movement of the valve 38 in the opening direction increases the fuel flow. The valve 38 therefore serves as a means for regulating the fuel flow supplementally to the regulation effected by variations in air velocity. The valve 38 is connected with a bellows 92 positioned in the chamber 82 and filled with a fiuid having a substantial coefficient of thermal expansion. Increased temperature or decreased pressure in the chamber 22 causes the bellows to expand and move the valve 38 in the closing direction, thus decreasing the rate of fuel supply. Decreased temperature or increased pressure in the chamber 32 causes the bellows to collapse and move the valve 38 in the opening direction, thus increasing the ra e of fuel supply.

In accordance with the invention it is necessary to provide means for indicating the rate of flow of fuel to the engine and a means for this purpose having certain important advantages is shown in Fig. 1. An enclosure 84 is provided having two chambers 88 and 88 at opposite ends thereof. These chambers are connected with the main fuel conduit respectively at opposite sides of the Jet system by means of conduits I88 and I82. The inner walls of said chambers are formed by flexible diaphragms I88 and 8, whose central portions are clamped between pairs of rigid discs I84 and I88. The two diaphragms I88 and H8 are connected for movement in unison by means of a central rod I I2. Inasmuch as the said movable walls are rigidly connected with each other they are adapted to exert a force toward the left which is a function of the diflerential between the pressures in the two chambers, and inasmuch as the two chambers are connected at opposite sides of the Jet system the pressure diflerential represents the drop in pressure across the jet system. which drop in pressure, for a given jet area, is a function of the rate of fuel flow through the main fuel conduit. In order that the beforedescribed pressure differential may be utilized, a suitable pressure transmitting device is employed, and as shown, this device comprises two concentric flexible bellows H4 and 8 which are carried by a partition H8 in the enclosure 84. The bellows are closed at their outer right ends by a movable wall I28 which is adjacent the movable wall I84. The space between the two bellows is entirely closed except for a duct I2I in the partition II8, the said duct being connected with a conduit I22. The conduit I22 leads to a suitable pressure responsive means such as a bellows I24 forming a part of an indicator unit shown more fully in other figures or the drawings and hereinafter described in detail, The space between the two bellows H4 and N8, the duct I2I, the conduit I22, and the bellows I24 is filled with a liquid having a low coeilicient of thermal expansion.

From the foregoing description it will be seen that the pressures in the chambers 98 and 88 are the same respectively as the pressures in the main fuel conduit at the upstream side of the Jet system and at the downstream side of the Jet system. The drop in pressure across the Jet system is proportionate to the rate of fuel flow, and therefore the pressure differential between the two chambers 96 and 88 is also proportionate to the rate of fuel flow. Inasmuch as the two walls or discs I84 and I86 are rigidly connected by the rod 2 the result is that the force applied to the end wall I28 of the two bellows H4 and H8 is proportionate to the said pressure differential and therefore proportionate to the rate of fuel fiow. This pressure is transmitted to the bellows I24 and tends to expand it. The space between the diaphragms I88 and H8 which is not occupied by the bellows H4 and H8 is filled with air or other suitable fluid and is sealed. While this gives a small unbalanced force on the end of bellows II4 due to the pressure of the sealed-in fluid, this pressure is constant and hence does not disturb the calibration of the system.

In accordance with the invention it is also necessary to provide means movable in accordance with the torque delivered by the internal combustion engine with which the apparatus is being used. As shown in the lower part of Fig. 1, the shaft I28 is the crank shaft of the engine or is directly connected to the crank shaft. The shaft V I28 carries a gear- I28 which meshes with a plurality of pinions I88, I88 carried by a substantially stationary spider I82. The pinions I88, I88 also mesh with an internal gear I84 which is connected with the airplane propeller or other device being driven by the engine. This gearing mechanism is part of the usual reduction gearing used between the engine and the propeller on modern aircraft.

The spider I32, while substantially stationary, is nevertheless rotatable within narrow limits. It carries .an outward projecting arm I88 which abuts against a longitudinally movable rod I38.

The rod I38 carries a piston I40 movable in and closely fitting a cylinder I42. A spring I44 within the cylinder tends to move the piston toward the right. Connected with theright end of the cylinder I42 is a conduit I48 connected with a suitable pressure responsive means such as a bellows I48 forming a part of the indicating unit before referred to. The space in the cylinder I42 at the right 01' the piston, the conduit I48, and the bellows I48 are fllled with a suitable liquid.

The torque delivered by the shaft I28 to the ring gear I34 istransmitted thru the spider I32 and this torque tends not only to rotate the ring gear in the counter-clockwise direction, but also 'width' of the groove I50 and which are therefore out of register with the groove when the latteris alined with port IN. The port I56 at the right is connected with a conduit I80 leading from a source of liquid under pressure and the port I58 at the left is connected with a drain conduit I82.

With the parts in the positions shown in Fig. 1 the ports I58 and I58 are closed. As lon as the force due to the torque, which acts to the right on rod I38 and piston I40, is balanced by the fluid pressure acting to the left on piston I40, then the rod I38 remains in the position shown. If the torque increaseshowever, or if by reason of leakage of liquid past the piston I40, the piston and the rod move toward the right, the port I53 will be uncovered, thus permitting liquid under pressure to flow from the conduit I80 through the conduit I54 and thence through the conduit I48 into the right end of the cylinder so as to move the piston and the rod toward the left at least suiliciently to close the port I56. If the movement of rod I38 to the right was due to leakage, the liquid so admitted will be just sufficient to restore the previously existing pressure in chamber HI and bellows I48. If the movement was due to a change in torque, then the liquid will be admitted until the pressure in chamber I is suilicient to balance the increased force. This increased pressure istransmitted to bellows I48.

causing expansion thereof .to indicate the increased torque. If the istcn'should be moved toward the left in response to a decrease in torque,

the port I58 will be opened. thus permitting some of the liquid to pass through the drain conduit I82 and permitting the piston to return to its normal position. This decreases the pressure in belto rotate the spider I32 in the clockwise direc- I lows I48 and causes contraction thereof to indicate the decreased torque.

The indicating unit is shown in Figs. 2 to 7 and will now be described in detail. It comprises a circular base I84 and an upwardly flanged top wall I 88. The members I84 and I88 areconnected by a plurality of upright posts I88, one of which is shown in Fig. 5. Surrounding the members I84 and I88 is a peripheral side wall I10 in which the assembly attached to base I84 is remo'vably held by two spring clips I12, I12. The spring clips I12. I12 are connected by screws to the base I84 and their upper ends project into apertures in the side wall I10. When the assembly is put in place the spring clips snap into the apertures in the side wall, but'the assembly can be removed by manually pushing the springclips inward. Resting on the upward extending annular flange of the top wall I88 is a glass cover I14 which is held in place on a panel I15, which may be part of the dashboard of an aircraft, by a ring I18 connected with the panel I15 by means of screws I11, I11.

The bellows I48 which is responsive to the torque exerted by the engine is carried by a plug I18 :tlttlng an aperture in the base I64." For visually indicating the torque of the engine there is provided an indicator or needle 200 operable l by the bellows I48. This needle can be variously operated and one suitable means for this purpose will now be described.

The upper end of the bellows I48 is closed by a movable yoke I which is U-shaped in cross section as shown in Fig. 2. Carried by the plu I18 is a cylinder I82 with an apertured p ll through which extends a rod I84. The rod I84 has threaded engagement at its upper end with the yoke I80 and at its lower end is provided with a head I88, which is guided for vertical movement in the cylinder. Acompression coil spring I88 within the cylinder I82 abuts at the top against the top wall of the cylinder and at the bottom against the head I86. The head 'I88'has a deep slot which provides communication to the interior of the cylinder from the conduit I48 and the top wall of the cylinder is provided with an aperture which provides communication with the interior of the bellows. It will be seen that fluid pressure within the bellows tends to move the yoke I80 upward but that this upward movement is opposed by the coil sprin I88. The movement of the yoke is proportionate to the amount of the torque exerted by the engine; 1

The two upstanding legs oi the yoke I80 are provided with vertical slots I80, I80 through which extends a horizontal shaft I82. The shaft I82 is rotatable in bearings carried bybrackets I83, I83 dependin from the top plate I68. It will be seen that the shaft I82 by reason of its engagement with the walls of the slots in the yoke serves to guide the yoke for vertical movement and to limit its vertical movement within certain predetermined limits. The left leg of the yoke I80, as viewed in Fig. 2, carries a vertical rack I84 which meshes with a pinion I88 rotatably mounted on the shaft I82. Connected with the pinion I88 and rotatable therewith is a bevel gear I88. The bevel gear I88,meshes with a bevel gear 200 which is carried by a rotatable sleeve 202 extending upward through the top wall I88. At the upper end of the sleeve 202 is a hub 204 carrying indicator needle 208 which is positioned between the wall I88 and the glass cover I14. The needle 208 is adapted to cooperate with an arm:- ate scale 208 on the top face of the wall I88, and

' 7 it will be seen that the readings of the needle 206 on the scale 208 represent the amount of the torque exerted by the engine.

The beforementioned bellows I24, which is responsive to the rate of fuel flow, is carried by a plug 2I0 in an aperture in the base I84 and pressure is transmitted to the interior of the bellows from the conduit I22 through an aperture in the saidpiug.

A second indicator or needle is provided which is operated or controlled in part by the bellows I24. This second needle is also controlled in part by the torque responsive bellows I48, so that the needle visually indicates efllclency of the engine, instead of indicating the total rate of fuel flow. The construction is such that the needle ind-icates only so much of any increases or decreases in fuel flow as are not directly proportionate to increases or decreases in torque. The means for operating or controlling the abovementioned second needle will now be described.

The bellows I24 is closed at the top by a member 2I2 having a deep conical recess therein, a bearing element 2 being provided at the bottom of the said conical recess. An arm 2I6 engages at one end with the bearing element 2I4 and is pivotally connected with the yoke I for movement about a horizontal axis. The right hand leg of the yoke I80, as shown in Fig. 2, carries a bearing bushing 2I8 within which is mounted a pivot pin 220 which is fixedly connected with the said arm 2| 6. The vertical position of pin 220 varies with the torque, since it is positioned by bellows 48. The arm 2I8 has a surface 222, shown in dotted lines in Fig. 3, which is normally vertical or substantially so, and which extends approximately through the axis of the pivot pin 220. Mounted on the shaft I92 is a lever 224, the lower end of which is in contact with the beforementioned surface 222 on the arm 2 I 6. The vertical position of the lower end of lever 224 is substantially constant. Therefore, the vertical distance between pin 220 and the lower end of lever 224 is a measure of the torque developed by the engine. The range of movement of the surface 222 with respect to the engaging point on the lever 224 is determined by the length of the slots I90, I90. The construction is such that the lever 224 always engages the surface 222 below the pivotal axis at 220.

A coil tension spring 226 is connected with the upper end of lever 224 and with a stud 229 projecting downward from the top wall I66. This spring tends to rotate the lever 224 in the clockwise direction, and thereby holds the lower end of lever 224 in engagement with the surface 222. The lever 224 is fixed on the shaft I92 for rotation therewith.

Shaft I92 carries a bevel gear 228 meshing with a bevel gear 230 carried by a vertical shaft 232. The shaft 232 is mounted within the bushing 202 and carries at its upper 'end a hub 234 with a needle or pointer 238 thereon. The needle 236 is positioned in the space between the wall I68 and the top cover I I4 and is above the needle 206. The top wall I88 is provided with a scale 238 with which the needle cooperates. The pointer 236 is biased y spri g 26 to its full-scale position. As explained-in detail below, the reading of the needle 236 with respect to the scale 238 indicates the efllciency of the engine.

The pressure in bellows I 24, which, as previously described, is a measure of the rate of fuel flow to the engine, produces a force acting upwardly on the end of arm 2I-8, which is likewise a measure of the rate of fuel flow. This force provides a torque which tends to rotate arm 2I8 counterclockwise. For any given stable set of conditions, this torque is opposed by an equal and opposite clockwise torque acting through the lower end of lever 224 on surface 222. The moment arm of this clockwise torque about the pivot 220 is proportional to the torque developed by the engine, as previously explained. Therefore, it may be stated that the force producing this clockwise torque about pivot 220 must be proportional to the fuel flow to the engine and inversely proportional to the torque developed by the engine. However, this force is proportional to the deflection of the spring 228 from its normal position and hence to the defiection of pointer 238 from its full-scale reading. It therefore follows that the deflection of pointer 238 from its full-scale position is proportional to the fuel flow to the engine and inversely proportional to the torque. In other words, the deflection of the pointer 238 from its zero position is an indication of the torque developed per unit fuel flow. If the engine speed is held constant, as is usually the case in modern aircraft engines, which are equipped with governors which vary the propeller pitch to hold the engine speed constant, then the torque developed per unit fuel flow is a measure of the useful power developed per unit fuel flow, or of the efilciency of the engine.

Means is provided, preferably as a. part of the indicator unit, whereby the operator can readily adjust the fuel-air ratio in order to attain maximum efllciency, as indicated by the needle 236 on the scale 238. For this purpose there is provided a knob 240 on a shaft 242 which extends downward through the glass cover I14 and the top wall I86 into engagement with a valve plug 244 in an aperture in the base I64. These parts are shown most clearly in Fig. 6. Connected with the valve plug 244 is conduit 248 which communicates at its other end with the chamber 42 in the pressure meter 44. The valve plug 244 has a central aperture 248 with lateral apertures 250, 250 communicating with the interior of the indicator unit, which is vented to the atmosphere as indicated at 25I. The shaft 242 is threaded into the end of the plug 244, as indicated at 252, and is provided with a needle valve 254 adjacent the apertures 250, 250. A suitable device on the shaft 242 prevents the shaft from being unscrewed sufliciently to entirely disengage the threads at 252, and this may be a split washer 256 entering an annular groove in the shaft. The knob 240 is removable so that the inner assembly may be removed from casing I10. The valve 254 is initially in position to entirely close the apertures 250, 250 but subsequently the valve 254 canbe withdrawn suificiently to open the apertures 250, 250 to whatever extent may be required.

The engine efllciency indicator to which this invention more particularly relates is ordinarily not used until after take-off and until after the airplane has reached the cruising altitude which has been decided upon. Then the propeller and the throttle are adjusted to provide the rate of propeller rotation and the cruising speed that are deemed desirable. Under these conditions the needle 206, controlled and operated in the manner already described, will indicate the amount of torque being exerted by the motor, which will be assumed to have an intermediate value as indicated in Fig. 7. The mixture control unit 60 will ordinarily be in the lean position with the duit 62.

' aesopaa fuel flowing to the iet system through the con- With may be assumed that the rate of fuel flow is greater than that representing maximum efilciency. The pilot or the flight engineer will then reduce the fuel-air ratio to attain maximum efficiency. This is done by turning the knob 240 to slightly open the valve 264 and permit air to flow inward'through the apertures 260. 260, the aperture 248 and the conduit 246, to the high suction or-low pressure. chamber 42 of the pressure.

meter 44. Air entering the apertures 256, 260 from the interior of the indicating unit is replaced by air entering the said unit through the apertures in which are entered the-detents I12. I12, or through the vent 26l. The entry of air into the chamber 42 increases the pressure in th said chamber and. reduces the pressure differential tending to move the valve 30 in the opening direction. This permits the valve 80 to move in the closing direction thus reducing the flow of fuel to the nozzle 26. If the'reduction in the rate of fuel flow increases the efficiency, then the pointer 236 moves to the left along scale 236, and the pilot continues to open the valve 264 until the needle 236 gives a -maxlmum reading on the scale 236, this maximum reading representing maximum efficiency.

The reduction in the rate of fuel flow not only increases the efficiency but it may also reduce the torque exerted by th engine, as indicated by the reading of the needle 206 on the scale 208. However. the construction that has been described is such that the movement of the needle 236 with respect to the scale 238 indicates only so much of the reduction in the rate of, fuel flow as represents increased efilciency. and there is no change in reading resulting from that part of the reduction in fuel flow corresponding to reduced torque. Any reduction in torque causes the yoke I80 to move downward carrying with it the pivot pin 226. As the axis of the pivot pin 226 moves downward the moment arm of the force applied by the spring 226 through the lever 224 to the arm M6 is correspondingly reduced. This reductionin moment arm causes a reduction in the clockwise torque applied-to the arm 2i6 which reduction is proportionate to the .decreased torque. This reduced clockwise torque counterbalances so much of the reduction in the counter-clockwise torque produced by the bellows I24 as results from decreased fuel flow corresponding to decreased torque. The net result is that any movement of the needle 236 toward the right directly indicates decreased eiliciency, and does not represent any reduction in fuel flow corresponding to I decreased torque.

Since the efficiency meter described does not take into account the engine speed nor the position of the mixture control 66, the position of needle 236 does not indicate efficiency in terms of power output per unit fuel flow or any other fixed units. However, for a given position of. the mixture control and for a given engine speed,'both of which remain fixed for long periods on modern aircraft, the position of needle 236 relative to scale 236 is a measure of the efficiency of the engine. When, under such conditions, the knob 240 is adjusted to make needle 236 move as far as maximum possible efficiency. I

After the described adjustment in the ratev of fuel flow has been made by means of the knob 240', so as to provide maximum efllciency as indithe' airplane operating as described, it v l cated by the needle 236, the throttle may be opened to restore the torque to its original value and when this is done the carburetor acts automatically to maintain the same or substantially 5 the same ratio of fuel flow to air flow. The pressure in the bellows I24 is increased proportionately to the increased fuel flow but the increased torque gives the spring 226 an increased mechanical advantage with the result that an increased clockwise torque is appliedto arm 216 which counterbalances the increased counter-clockwise torque due to the increase of pressure in bellows I24. The needle 236 will not move because of the increased torque, except as the increased torque may involve an incidental change in efficiency. After the restoration of the torque to its orginal value the operator should again check the efficiency by adjusting the knob 246 to make sure that the reading of the eiiiciency indicator needle 236 is at a maximum position indicating maximum efficiency.

If operating conditions from time to time require increases or decreases in torque, such in-'- creases ,or decreases do not affect the reading of the needle 236 except as such increases or decreases may result in changes in efiicienc'y. After each major change in torque the knob 24!! should be adjusted to make sure that the engine is operating at maximum efilciency.

of fuel flow effected by means of the knob 243 must be governed by observation of the needle 236 and discontinued when the needle shows maximum efficiency. Too great areduction in the rate of fuel would result in too lean a mixture and in decreased efilciency which would cause the needle 236 to shift toward the right from its maximum efficiency position. i

It has been stated that the mixture control valve will ordinarily be in its lean position when reductions in the rate of fuel flow ar made by means of the knob 246. By reason of the location of the mixture control valve in the lean position, it may sometimes be found that the mix- 5 ture is already too lean and that any further leaning of the mixture by means of the knob 246 results in decreased efliciency rather than increased eihciency. This would instantly be observed by the operator, as he would find that the leaning of the mixture by means of the knob 24!! would cause the needle 236 to move toward the right instead of toward the left thus indicating a decrease in efficiency, rather than an increase. In

this event the operator should shift the mixture control valve to its rich position, and then operate the knob 243 to lean the mixture to whatever extent might be necessary to attain maximum efiiciency.

While I have shown and described a certain 00 preferred embodiment of my invention, other embodiments thereof will readily occur to those skilled in the art, and I therefore intend my invention to be limited only by the appended claims.

I claim as my invention:

1. In an efilciency indicator for an internal combustion engine, the combination of means for indicating the maximum efllciency of the engine in terms of torque developed per unit of fuel flow to the engine, and means for preventing variations in the action of the first said means resulting from changes in engine torque.

2. In an efficiency indicator for an internal combustion engine, the .combination of means responsive to the torque of the engine and in- 7 dependent of engine speed, means responsive to It will be clear that any reduction in the rate ll the rate of flow of fuel to the engine. and a movable needle controlled by both of the said means.

3. In an efficiency indicator for an internal combustion engine, the combination of means responsive to the rate of flow of fuel to the engine, a needle operably connected with the said fuel flow responsive means. and means responsive to the torque of the engine and independent of engine speed for modifying the operative relationship between the said needle and the said fuel flow responsive means.

4. In an efficiency indicator for an internal combustion engine, the combination of means responsive to the torque of the engine and independent of engine speed, means responsive to the rate of flow of fuel to the engine, a needle operably connected with the fuel flow responsive means, and mechanism controlled by the torque responsive means for varying the extent of movement of the needle inversely with variations in the torque.

5. In an eiliciency indicator for an internal combustion engine, the combination of means responsive to the torque of the engine and independent of engine speed, means responsive to the rate of flow of fuel to the engine, a movable needle operatively connected with the fuel flow responsive means, and mechanism controlled by the torque responsive means for resisting the movement of the fuel flow responsive means to an extent inversely proportionate to the torque.

6. In an efliciency indicator for an internal combustion engine, the combination of means responsive to the rate of flow of fuel to the engine, a needle operatively connected with the said fuel flow responsive means, a spring opposing the action of the fuel flow responsive means, and means responsive to the torque of the engine for changing the mechanical advantage of the spring in accordance with changes in torque.

'7. In an emciency indicator for an internal combustion engine, the combination of means responsive to the rate of flow of fuel to the engine, a needle operably connected with the said fuel flow responsive means, a spring opposing the action of the fuel flow responsive means, and means responsive to the torque of the engine for increasing the mechanical advantage of the spring in accordance with increases in torque and for decreasing the mechanical advantage of the spring in accordance with decreases in torque.

8. In an efficiency indicator for an internal combustion engine, the combination of means responsive to the rate of flow of fuel to the engine, a needle operably connected with the said fuel flow responsive means, a spring opposing the action of the fuel flow responsive means, and means responsive to the torque of the engine for changing the mechanical advantage of the spring in inverse proportion to changes in torque.

9. A fuel system for an internal. combustion engine comprising in combination, means for indicating the maximum efficiency of the engine, means for preventing variations in the action of the first said means resulting from changes in engine torque, and manually operable means for adjusting the rate of fuel flow to effect maximum efficiency as indicated by the first said means.

10. A fuel system for an internal combustion engine comprising in combination, means responsive to the torque of the engine, means responsive to the rate of flow of fuel to the engine,

a needle operably connected wlth'the fuel flow responsive means, mechanism controlled by the torque responsive means for varying the extent of movement of the needle inversely with variations in the torque, and manually operable means for adjusting the rate of fuel flow to effect maximum efficiency as indicated by the said needle.

11. A fuel system for an internal combustion engine comprising in combination, means responsive to the rate of flow of fuel to the engine, a needle operatively connected with the said fuel flow responsive means, a spring opposing the action of the fuel flow responsive means, means responsive to the torque of the engine for changing the mechanical advantage of the spring in inverse proportion to changes in torque, and manually operable means for adJusting the rate of fuel flow to effect maximum efficiency as indicated by the said needle.

12. A fuel system for an internal combustion engine, comprising in combination, a passage including a venturi for air flowing to the engine for combustion purposes, a pressure meter having two chambers and a flexible diaphragm separating the chambers, conduits connecting the Venturi entrance and throat with the respective chambers, a valve operable by the diaphragm and controlling the flow of fuel to the engine, the said valve being moved in the opening direction by an increase in the pressure diflerential between the two chambers and being moved in the closing direction by a decrease in the said differential, means responsive to the torque of the engine, means responsive to the rate of flow of fuel to the engine, a, needle operably connected with the fuel flow responsive means, mechanism controlled by the torque responsive means for varying the extent of movement of the needle inversely in accordance with variations in torque, and manually operable means for decreasing the pressure differential between the two chambers to move the valve in the closing direction and thus reduce the rate of fuel flow to effect maximum efficiency as indicated. by the said needle.

13. A fuel system for an internal combustion engine, comprising in combination. a passage including a venturi for air flowing to the engine for combustion purposes, a pressure meter having two chambers and a flexible diaphragm separating the chambers, conduits connecting the Venturi entrance and the throat thereof with the respective chambers, a valve operable by the diaphragm and controlling the flow of fuel to the engine, the said valve being moved in the opening direction by an increase in the pressure diflerential between the two chambers and being moved in the closing direction by a decrease in the said diflerential, means responsive to the torque of the engine, means responsive to the rate of flow of fuel to the engine. a needle operably connected with the fuel flow responsive means, mechanism controlled by the torque responsive means for varying the extent of movement of the needle inversely in accordance with variations in torque, and manually operable means for admitting air to the chamber having the lower pressure to decrease the pressure differential between the two chambers to move the valve in the closing direction and thus reduce the rate of fuel flow to effect maximum efliciency as indicated by the said needle.

14. An efficiency indicator unit for an internal combustion engine, comprising in combination, a

- means movable in response to pressure representneedle movable by the said means to indicate the amount of torque, a means responsive to pressure representing the rate of fuel flow to the engine, a second needle operably connected with the fuel flow responsive means, and mechanism operable in part by the torque responsive means for varying the movements of the second needle inversely in accordance with variations in torque.

15. An efflciency indicator unit for an internal combustion engine, comprising in combination, a means responsive to pressure representing the torque exerted by the engine, a needle operable by the torque responsive means to indicate the amount of torque, a means responsive to pressure representing the rate of fuel flow to the engine, a needle operably connected with the fuel flow responsive means, and mechanism controlledby the torque responsive means for varying the extent of movement of the second said needle.

16. An efficiency indicator unit for an internal combustion engine, comprising in combination,-

a means responsive to pressure representing the torque exerted by the engine, .a needle operable by the torque responsive means to indicate the amount of torque, a means responsive to pressure representing the rate of fuel flow to the engine, a needle operably connectedwith the fuel flow responsive means, and mechanism controlled by the torque responsive means for varying theextent of movement of the second said needle inversely in accordance with variations in torque. 17. An efliclency indicatorunit for an internal combustion engine, comprising in combination,

a means responsive to pressure representing the torque exerted by the engine, a pivoted needle operable by the said means to indicate the amount of torque, a means responsive to pressure representing the rate of fuel flow to the engine, a needle operably connected with the fuel flow responsive by the torque responsive means to indicate the amount of torque, a means responsive to pressure representing the rate of fuel flow to the engine, a needle operably connected with the fuel flow responsive means, and mechanism controlled by almost gearing connecting the needle with the for operating the former in accordance with'movement of the lattervto indicate the amount of the torque responsive -means for resisting the movement of the fuel flow responsive means to an extent varying inversely with the torque.

19. An efiiciency indicator unit for an internal combustion engine, comprising in combination, a yoke movable in response to pressure representing the torque exerted by the engine, a pivoted needle, gearing connecting the needle with the yoke for operating the former in accordance with movement of the latter to indicate the amount of torque, a means responsive to pressure representing the rate of fuel flow to the engine, a second pivoted needle, gearing for operating the second needle, and mechanism connecting the fuel flow responsive means with the second gearing to operate the second said needle, the said mechanism being carried in part by the yoke whereby movement of the yoke varies the operation of the second said needle.

20. An efllciency indicator unit for an internal combustion engine, comprising in combination, a

yoke movable in response to pressure representing the torque exerted by the engine, a pivoted needle,

torque, a means responsive to pressure representing the rate of fuel flow to the engine, a second pivoted needle, gearing connected with the fuel flow responsive means for operating the second needle, an arm pivoted to the movable yoke and engaging the fuel flow responsive means to oppose the movement thereof, and a spring actuatedlever pivoted for rotation about a fixed axis and enga ing the said arm to rotate it in the opposing direction, the engagement of the said lever with the said arm being at varying distances from the movable axis of the latter so that the arm exerts varying pressures on the fuel flow responsive means.

21. An eiliciency indicator unit for an internal combustion engine, comprising in combination,

a means movable in response to pressure representing the torque exerted by the engine, an indicator needle movable by the said means to indicate the amount of torque, a means responsive to pressure representing the rate of fuel flow to the engine, a second needle operably connected with the fuel flow responsive means, mechanism operable in part by the torque responsive means for varying the movements of the second needle inversely in accordance with variations in torque, and manually operable means for adjusting the rate of fuel flow to effect maximum efficiency as indicated by the second said needle.

22. An efliciency indicator unit for an internal Justing the rate of fuel flow to effect maximum efilciency as indicated by the second said needle.

23. An efiiciency indicator unit for an internal combustion engine, comprising in combination, a yoke movable in response to pressure representing the torque exerted by the engine, a pivoted needle, gearing connecting the needle with the yoke for operating the former in accordance with movement of the latter to indicate the amount of torque, a means responsive to pressure representing the rate of fuel flow to the engine, a second pivoted needle, gearing for operating the second needle, mechanism connecting the fuel flow responsive means with the second gearing to operate the second said needle, the said mechanism being carried in part by the yokewhereby movement of the yoke varies the operation of the second said needle, and manually operable means for adjusting the rate of fuel flow to effect maximum eiflciency as indi cated by the second said needle.

24. In a fuel supply system for an internal combustion engine, the combination of a main fuel conduit including a jet means, two chambers connected with the main fuel conduit at the respective sides of the jet means, movable means associated with the said chambers so that pressure in one chamber tends to move it in one direction and pressure in the other chamber tends to move it in the opposite direction, the

acsaeas 15 said means being therefore movable in response to the differential between. the pressures in the two chambers, and means for transmitting the pressure exerted by the said movable means.

25. In a fuel supply system for an internal combustion engine, the combination or a main fuel conduit including a Jet means, two chambers connected with the main fuel conduit at the respective sides of the Jet means, movable means associated with the said chambers so that pressure in one chamber tends to move it in one direction and pressure in the other chamber tends to move it in the opposite direction, the said means being therefore movable in response to the differential between the pressures in the two chambers, a bellows positioned to be moved in the collapsing direction by movement of the said movable means, and a conduit connected with the interior of the bellows and adapted to transmit fluid pressure to 'a pressure responsive means.

26. In a fuel supply system for an internal combustion engine, the combination of a main fuel conduit including a jet means, two chambers connected with the main fuel conduit at the respective sides of the Jet means, each chamber having a movable wall and the two wall being so positioned that the pressures in the respective chambers tend to move them in opposite directions, means for connecting the two movable walls for movement in unison in response to the differential between the pressures in the two chambers, and means for transmitting the pressure exerted by the said connected movable walls.

27. In a fuel supply system for an internal combustion engine. the combination of a main bers connected with the main fuel'conduit at the respective sides of the jet means, each chamber having a movable wall and the two walls being so positioned that the pressures in the -fuel conduit including a Jet means, two chamrespective chambers tend to move them in D- posite directions, means for connecting the two movable walls for movement in unison in response to thediiferential between the pressures in the two chambers, a bellows positioned between the two movable walls and movable by one of them in thecollapsing direction; and a conduit connected with the interior of the bellows and adapted to transmit fluid pressure to a pressure responsive means.

. 28. Apparatus for indicating the ratio between a first variable and a second variable, comprising a first lever fixed to a shaft, means biasing said shaft for rotation in a predetermined sense, a second lever engaging said first lever at a predetermined point thereon spaced from said shaft, means responsive to said first variable for applying a torque to said second lever so as to transmit a force to said first lever in a sense to oppose said biasing means, a pivot for said second lever, means responsive to said second variable for shifting said pivot so as to vary the moment arm of said torque inversely as said second variable, and means for indicating the rotation of said shaft. LEIGHTON LEE, II.

, REFERENCES CITED The following references are of record in the Jackes June 17, 1947 

